The present invention relates to an apparatus for coating or applying photoresist material onto a wafer or substrate.
Generally, the coating material is in liquid state. A conventional photoresist material having a protection group such as t-BOC and acetal does not harden easily when compared to a photoresist material for use with the ArF laser. As a result, the photoresist hardening phenomenon, which causes photoresist powder drops or coating failure during a coating process, generally does not occur when such a conventional photoresist material is used in a coating apparatus having a conventional solvent bath. However, it is somewhat difficult to use the conventional photoresist material including a polyhydroxystyrene-based polymer for forming an ultra fine pattern because it absorbs the ArF laser (193 nm wavelength). Accordingly, the researchers have been trying to find a replacement photoresist material that would be suitable for use with the ArF laser.
Generally, a suitable polymer for the ArF laser should be transparent, have good tolerance to dry etching, and be good adherent. A photoresist material having an aromatic ring structure that is for KrF laser has good tolerance to dry etching, but the aromatic ring structure absorbs 193 nm wavelength light. As a result, a promising photoresist material for the ArF laser has been developed by adding an alicyclic group structure to a metahacrylate polymer.
FIG. 1 is a simplified cross-sectional view showing a conventional apparatus for coating a photoresist material onto a substrate or wafer.
The apparatus includes a nozzle 11, a solvent bath 25, a lid 13, a solvent supplying port 15, a solvent pipeline 17, a solvent trap 19, a solvent fume trap 21 and a solvent drain member 23. Here, the nozzle 11 is used to inject the photoresist material onto a wafer (not shown). The lid 13 has one or more nozzle holders having a nozzle tip cover 13C for housing the nozzle 11. The nozzle holder exposes only the edge of the nozzle 11. Also, the solvent pipeline 17 is provided under the lid 13 to guide the solvent supplied to a solvent bath 25 to the solvent drain member 23. Here, the solvent trap 19 is configured to hold solvent and prevent the photoresist residue in the nozzle 11 from being hardened, e.g., by using the fumes from the solvent being held in the solvent trap 19. The solvent supplying port 15 is provided adjacent to the solvent trap 19 to supply the solvent to the solvent bath 25. The solvent fume trap 21 is provided near to the top of the solvent pipeline 17 to store fumes generated from the solvent trap 19. Accordingly, both the solvent trap 19 and the solvent fume trap 21 are configured to prevent the photoresist residue in the nozzle 11 from being hardened.
According to the above apparatus, the solvent fume trap 21 does not effectively secure the fumes. Since the solvent trap 19 is provided at a significant distance away (e.g., 45 mm) from the lower surface of the nozzle 11, it is difficult to effectively prevent the photoresist material from being hardened. As a result, the coating failure may occur due to discoloring of the photoresist material and/or dropping of the hardened photoresist material (i.e., photoresist powders) on the wafer during the coating process.